@Serika – just that what Peter said. But in some situations it does not work at all or yield "wrong" results. It all depends how many styles of your font family are available or fell in the category "Bold" weight.

One positive example is "Times New Roman" where four variants are present: "Regular", "Italic", "Bold" and "Bold Italic".

One intermediate example is "Warnock Pro" where more than four font variants are in the family.It works for you to set "Regular" to "Bold" and back, but it won't work setting "Light" to "Bold" with the keyboard shortcuts.

Also, you could not get "Semibold" if you like to.

One negative example out of many is "Hiragino Kaku Gothic Pro", where there is no "Regular" or "Bold" face, just "W3" or "W6". With that font you cannot switch from "W3" to "W6" with a keyboard shortcut.

(And there are thousands of other fonts out, that are not working the way you are expecting it).

Conclusion:Always work with Character Styles.And apply Keyboard Shortcuts to them.